1. Field of the Invention
The present invention relates to an electromagnetic switch for starters.
2. Description of the Related Art
A conventional electromagnetic switch is provided by, for example, a U.S. Pat. No. 6,204,742 B1.
This electromagnetic switch has a construction in which a molding cap equipped with both of a motor terminal and a battery terminal is fastened to a switch case in the axial direction by caulking ends extending from the switch case. The caulking ends are made to locate at positions around an open end of the molding cap to be connected with the switch case. The caulking ends consist of two or more caulking portions arranged between the motor terminal and the battery terminal in the circumferential direction of the open end of the molding cap. This configuration of the caulking portions makes the electromagnetic switch compact, while still maintaining a larger center distance between the motor and battery terminals.
In the case of the foregoing conventional electromagnetic switch, however, connecting the molding cap and the switch case can be realized by means of only two or more caulking portions. That is, the molding cap is caulked partially, not caulked at the entire circumference of the molding cap. In this partial caulking structure, there is a possibility that the remaining circumferential connection portions other than the caulking portions may cause a slight gap between the connections of the switch case and the molding cap. If such a gap is formed between the switch case and the molding cap, there is a fear that foreign materials, such as moisture and dust may intrude into the switch through the gap.
In addition, if foreign materials remain in one or more apertures formed between the remaining circumferential connection portions other than the caulked portions and are deteriorated for a long time, the caulking pressure may be lowered from an initial amount. When the caulking pressure reduces unexpectedly, there may be caused a relative positional shift between the switch case and the molding cap. Such a positional shift, if any, will bring about a positional shift of a fixed contact from a movable contact in the molding cap. If such a case occurs, the movable contact is in contact with the fixed contact in a one-sided contact fashion, whereby the contacts may be worn away extraordinarily.